how do you get your curves to be so perfect.
practice i suppose
the lines are actually scratchy-sketch lines. i'm told this is a bad habit, and professionals use a more "swooping" motion using their shoulder/elbow, not twisting or moving the hand at all. i'm not sure if it is used for all forms of drawing, but i've seen it used for sketch-periods. i'm not able to do it properly though. (i've been told the best practice is to use five sheets of scratch paper, and just fill them up with ovals using your shoulder/elbow)
the stabilizer on paint tool sai is also set to 10 (i use ten or fiveteen for sketches and S-7 for lineart). it makes the lines "fade" more than anything
and it's also scaled. i typically draw with it being 33.33% zoomed out (my canvases are always 3840x2160, basically 1080p x2)